Wavelength estimation device, light-source device, image display apparatus, object apparatus, wavelength estimation method, and light-source control method

Abstract

A wavelength estimation device including a light detector to receive light emitted from a light source and an estimation unit. The estimation unit estimates a wavelength of the light based on an amount of light received by the light detector.

What is claimed is: 
     
       1. A wavelength estimation device, comprising:
 a light detector to receive unfiltered light emitted from a light source; 
 a detector to detect an ambient temperature of the light source; and 
 processing circuitry configured to estimate an oscillation wavelength of the unfiltered light when emitted from the light source, based on an amount of the unfiltered light received by the light detector, 
 wherein the processing circuitry is further configured to estimate the oscillation wavelength of the light based on the amount of light received by the light detector and the ambient temperature detected by the detector. 
 
     
     
       2. The wavelength estimation device according to  claim 1 , further comprising a signal processor to temporally average a signal according to the amount of light received by the light detector to generate an average amount of light received by the light detector,
 wherein the processing circuitry is further configured to estimate the oscillation wavelength of the light based on the generated average amount. 
 
     
     
       3. The wavelength estimation device according to  claim 1 ,
 wherein the processing circuitry is configured to estimate the oscillation wavelength of the light based on a formula of λ=λ (0) +α×(T a −T a   (0) )+β×(P−P (0) ), 
 where 
 λ is the wavelength of the light, 
 λ (0)  is a reference wavelength, 
 α is a temperature coefficient, 
 T a  is a current ambient temperature, 
 T a   (0)  is an ambient temperature on measurement of the reference wavelength, 
 β is light-amount coefficient, 
 P is a current amount of light emission, and 
 P (0)  is an amount of light emission on measurement of the reference wavelength. 
 
     
     
       4. The wavelength estimation device according to  claim 1 ,
 wherein the reference wavelength λ (0)  is a virtual wavelength with P (0)  being 0 W. 
 
     
     
       5. The wavelength estimation device according to  claim 3 ,
 wherein the light source includes a semiconductor laser that oscillates in a multi-longitudinal mode, and 
 wherein the reference wavelength is a wavelength obtained by weighted-averaging wavelength components having intensities ranging from Id to an intensity of −20 decibel (dB) relative to Id, 
 where Id is a peak intensity of the light emitted by the semiconductor laser. 
 
     
     
       6. A light-source device, comprising:
 the light source including a light-emitting element to emit light; and 
 the wavelength estimation device according to  claim 1 , which is configured to estimate the oscillation wavelength of the light when emitted from the light-emitting element. 
 
     
     
       7. The light-source device according to  claim 6 , further comprising a drive circuit to drive the light source,
 wherein the detector of the wavelength estimation device includes a temperature sensor disposed at a position at which an ambient temperature detected by the temperature sensor is insusceptible to heat generated by the drive circuit. 
 
     
     
       8. The light-source device according to  claim 6 , further comprising:
 a plurality of light sources constituted by the light source and at least another light source, the plurality of light sources including a plurality of light-emitting elements having different light-emission wavelength bandwidths; and 
 an optical system to combine light emitted from the plurality of light sources and separate the combined light, wherein 
 the processing circuitry is further configured to set amounts of light emission of the plurality of light-emitting elements based on wavelengths of the light emitted from the plurality of light sources, the wavelengths having been estimated by the wavelength estimation device, 
 wherein the light detector of the wavelength estimation device is disposed in an optical path of light separated by the optical system. 
 
     
     
       9. The light-source device according to  claim 6 ,
 wherein the light-emitting element is disposed in a housing including a light-transmission window member, 
 wherein the light-transmission window member separates light emitted from the light-emitting element into transmitted light and reflected light, and 
 wherein the light detector of the wavelength estimation device includes a light-receiving element disposed in the housing to receive the reflected light. 
 
     
     
       10. The light-source device according to  claim 9 , further comprising:
 a plurality of light sources constituted by the light source and at least another light source, the plurality of light sources including a plurality of light-emitting elements having different light-emission wavelength bandwidths; and 
 a plurality of light detectors corresponding to the plurality of light-emitting elements, wherein 
 the processing circuitry is further configured to set amounts of light emission of the plurality of light-emitting elements based on wavelengths of the light emitted from the plurality of light-emitting elements, the wavelengths having been estimated by the wavelength estimation device. 
 
     
     
       11. The light-source device according to  claim 6 ,
 wherein the light-emitting element is an end-surface light-emitting semiconductor laser having a first end surface and a second end surface, 
 wherein the semiconductor laser is disposed in a package including a light-transmission window member through which light emitted from the first end surface of the semiconductor laser passes to an outside of the package, and 
 wherein the light detector of the wavelength estimation device includes a light-receiving element disposed in the package to receive light emitted from the second end surface of the semiconductor laser. 
 
     
     
       12. The light-source device according to  claim 11 , further comprising a dimming element disposed in an optical path between the second end surface of the semiconductor laser and the light-receiving element in the package. 
     
     
       13. An image display apparatus comprising:
 the light-source device according to  claim 6 , 
 an image forming element to form an image by light emitted from the light-source device; and 
 a screen to be irradiated with the light forming the image. 
 
     
     
       14. An object apparatus comprising:
 the image display apparatus according to  claim 13 , further including a projector to project light having passed through the screen to a light-transmission window member; and 
 an object mounted with the image display apparatus. 
 
     
     
       15. The object apparatus according to  claim 14 ,
 wherein the object is a mobile object. 
 
     
     
       16. A wavelength estimation method, comprising:
 receiving unfiltered light emitted from a light source; 
 detecting an ambient temperature of the light source; and 
 estimating an oscillation wavelength of the unfiltered light when emitted from the light source based on an amount of the unfiltered light received in the receiving step, 
 wherein the estimating step includes estimating the oscillation wavelength based on the received amount of light and the detected ambient temperature. 
 
     
     
       17. A light-source control method, comprising
 turning on a plurality of light sources having different light-emission wavelength bandwidths to emit light; 
 detecting an ambient temperature of the plurality of light sources; 
 receiving, by a light detector, the light emitted from the plurality of light sources, the received light being unfiltered; 
 estimating oscillation wavelengths of the unfiltered light when emitted from the plurality of light sources based on an amount of the unfiltered light received in the receiving step; and 
 setting amounts of light emission of the plurality of light sources based on an estimation result of the estimating step, 
 wherein the estimating step includes estimating the oscillation wavelengths based on the received amount of light and the detected ambient temperature.